Cooking food with steam has long been recognized as a process which is not only efficient in terms of energy consumption, but which has the additional benefit of relatively low removal of nutrients from the food. Because available steam cooking systems have tended to be rather large and complex, steam cooking has for the most part been limited to high volume operations such as institutional cooking.
More recently, there has been increasing interest in steam cooking in restaurant applications. Steam cooking is particularly useful when frozen foods are involved, because it is entirely practical to have several different foods in a single container in which they may be cooked and also served to the customer. In response to this market, some equipment has been devised which is relatively compact, steam being generated by electric heaters and the entire apparatus being of a size small enough to serve as as a counter-top appliance. Because steam generation with electrical heating is a relatively slow and expensive process, however, alternative energy sources have come under consideration.
One obvious alternative energy source is gas, which is usually available in restaurants and institutions. However, available gas-fired equipment for generating steam is simply too large and cumbersome for use in steam cookers of a size that would be commercially acceptable. Moreover, the thought of a gas-fired steam cooker small enough to serve as a counter-top appliance has been dismissed as wholly impractical.